In an effort to further extend the number of targets for development of anti-retroviral agents, we are studying HIV-1 integrase inhibitors using in vitro assays using recombinant enzyme and short oligonucleotides corresponding to the proviral ends (LTR's). Integrase is a rationale target for inhibitor development because it is essential for viral replication. It is also encoded by HIV and does not have a cellular equivalent. Our laboratory has pioneered this research field and reported various families of inhibitors. Recently, the first class of selective HIV-1 integrase inhibitors with demonstrated antiviral activity related to integrase inhibition has been introduced in clinical trials. We are investigating these diketo acid (DKA) derivatives in collaboration with Dr. Terrence Burke (Laboratory of Medicinal Chemistry, CCR, NCI) and Dr. Vinay Pathak (Antiviral Drug Resistance Program, CCR, NCI). Our goals are to determine the structure-activity relationship for this new type of compounds, to elucidate the drug binding site(s) in the enzyme-DNA complex, and to discover agents with a greater therapeutic index and/or novel structural motifs. We found that azido derivatives of diketo acids are potent and selective anti-integrase inhibitors, and are antiviral. A patent application has been filed for these derivatives. We are also studying novel types of inhibitors that can prevent integration by binding to the proviral DNA ends as well as small peptide and nucleotide inhibitors. We are also studying the molecular interactions between integrase and its DNA substrate using enzyme-DNA crosslinking assays in order to model drug-enzyme-DNA interactions. We recently found a novel interaction between one of the viral DNA bases and the enzyme.